JP2023525881A - Overload protection in wind turbine installations using strain sensors - Google Patents

Abstract

A method (200) for controlling a wind power plant (10) with a rotor having at least one rotor blade (17), the method comprising measuring (210) the strain of the at least one rotor blade. , varying the pitch angle of the at least one rotor blade at least in part based on the measured strain of the at least one rotor blade (220); and measuring the strain of the at least one rotor blade. measuring strain in at least the region of the root portion of the rotor blade (17) by:

Description

The present disclosure relates to methods and wind power installations for controlling wind power installations. In particular, the method according to the present disclosure relates to the control of a wind power installation, in which at least the strain in the root region of the rotor blades of the wind power installation is measured. Furthermore, the method of the present disclosure relates to changing the pitch angle of the rotor blades of a wind power installation, where in particular overloading of generators and/or converters of the wind power installation is prevented.

A wind power plant converts wind energy into electrical energy. The wind exerts a force on at least one rotor blade of the rotor of the wind power installation, which converts the kinetic energy of the wind into kinetic rotational energy of the rotor. The rotor drives a generator that supplies electrical energy to the electrical grid. A generator typically produces an alternating voltage.

The force of the wind on the rotor blades varies over time, for example in relation to gusts, wind strength and wind direction. This changes both the electrical power produced and the frequency of the voltage produced by the generator and/or the current produced by the generator.

The converter makes it possible, starting from the voltage/current with variable frequency generated by the generator of the wind power plant, to supply the grid with a voltage/current with constant frequency.

For example, in a converter, an alternating voltage produced by a generator, having a variable frequency, can be converted into a direct voltage, where an energy accumulator, such as a capacitor, is for example an output voltage/power having a constant frequency. In order to supply the current, the electrical energy is temporarily stored on the basis of the DC voltage, which is also used in the converter.

The converter receives almost all the electrical energy of the generator with variable frequency, temporarily stores the energy in an energy accumulator, for example a capacitor, based on the generated direct voltage, and converts the alternating current with constant frequency into an alternating current with constant frequency. The generation of can supply electrical energy to the electrical grid.

In a doubly-fed asynchronous generator, the converter is arranged to supply part of the energy produced by the generator to the grid or direct part of the energy to the generator. good. The overall output voltage/total output current of the wind power installation at the grid terminals is the voltage produced by the generator/current produced by the generator and the voltage produced by the converter/produced by the converter. by which a constant frequency at the grid feed point can be guaranteed.

By using a doubly fed asynchronous generator, the converter can be made smaller. This is because only a portion of the total energy and total power flows through the converter.

In case of gusts and/or strong winds, the converters and/or generators of the wind power installation may become overloaded. Excessively strong winds and/or excessively strong gusts of wind cause an increase in the kinetic energy of the rotor of the wind power installation, which in turn can cause an increase in the generated electrical power of the generator. This can damage the generators of the wind power installation. The converter can also be damaged if the electrical power generated by the generator exceeds a limit value, for example if too much current flows through the semiconductor elements of the converter.

Therefore, the kinetic energy of the rotor and/or the kinetic power transferred from the rotor to the generator and/or the electrical power generated by the generator and/or the power flowing through the converter may be , must be restricted.

The output limitation described above can be achieved, for example, by adjusting the pitch angle of the rotor blades.

By adjusting the pitch angle, the force exerted by the wind on the rotor blades can be reduced, thereby reducing the kinetic power transferred. This reduces the kinetic rotational power of the rotor and reduces the electrical power generated by the generator. This prevents generator and/or converter overload.

If the pitch angle is adjusted too slowly, overload can no longer be prevented under certain circumstances.

If the pitch angle is adjusted too early, wind power that could have been converted to electrical power may be lost in some circumstances.

There is therefore a need for an improved method in order to change the pitch angle of the rotor blades as optimally as possible, which in particular effectively prevents overloading of the generator and/or converter. In doing so, wind power that could have been converted into electrical power by the wind power plant is not lost unnecessarily and/or damage to the generator and/or rotor blades is not caused.

According to one embodiment, a method of controlling a wind power plant with a rotor having at least one rotor blade is disclosed, the method comprising the steps of measuring the strain of the at least one rotor blade; and v. at least partially altering the pitch angle of the at least one rotor blade based on the measured strain of the blade, wherein the measurement of the strain of the at least one rotor blade causes at least one of the rotor blades to The strain in the root area is measured.

According to another embodiment, a wind power plant is disclosed, the wind power plant comprising a sensor for measuring the strain of at least one rotor blade of the wind power plant, and the strain of the at least one rotor blade measured by the sensor. a control unit configured to at least partially vary the pitch angle of the at least one rotor blade based on the control unit, the control unit controlling the wind power installation according to the method described above.

Further embodiments, details and advantages are disclosed according to the dependent claims, the further description and the drawings.

1 illustrates a wind farm installation according to an embodiment of the present disclosure; FIG. 1 illustrates a method of controlling a wind power plant according to the present disclosure; FIG.

A wind power plant converts the kinetic energy of the wind into electrical energy or converts kinetic power into electrical power. Power is understood as the energy consumed per unit time or the time derivative of the energy.

FIG. 1 shows a wind power plant according to an embodiment of the present disclosure.

The wind power installation 10 includes at least one rotor blade 17 driving the rotor 14 . The wind impinges on the rotor blades 17, thereby exerting a force on the rotor blades 17, which causes a torque in the rotor. This accelerates the rotor 14 and rotor blades 17 until equilibrium is achieved by torques acting in opposite directions. Such counteracting torque may be the torque of the generator 16, which converts kinetic rotational energy into electrical energy, and/or torque caused by friction.

The wind power installation 10 may include a converter 12, which in particular does not have a constant frequency generated by the generator 16 (the wind does not produce a constant rotation speed of the rotor 14). is used to realize/generate an alternating current with a constant frequency on the basis of an alternating current/voltage.

The wind power installation 10 may also include an anemometer 11 and/or a control installation 13 with which in particular the pitch angle of the rotor blades 17 can be open-loop controlled or closed-loop controlled. By adjusting the pitch angle of the rotor blades 17, the force exerted by the wind on the rotor blades can be varied. This changes the wind-generated torque of the rotor blades.

Likewise, the torque of the generator 16 and/or the transmission ratio of the rpm from the rotor 14 to the generator 16 can be varied, for example by adjusting gears.

The electrical power available for a given wind speed is limited. Excessively high wind speeds can damage wind turbines. For example, a generator may be overloaded by kinetic power and/or a converter may be overloaded by electrical power. Overloading a converter/generator in this disclosure means exceeding the maximum nominal power output towards and/or starting from the converter/generator.

The wind power plant 10 according to embodiments of the present disclosure includes at least one strain sensor 15 at the root of the rotor blades 17 .

If the wind power installation 10 is in full load mode during high wind phases, overloads occurring in the form of gusts with high wind speeds can lead to damage to the converter 12 . If the facility's closed-loop control responds to this overload too slowly, the electrical energy produced by the generator 16 in the converter 12 may not be properly processed. This results in short-term operation of the transducer beyond its output parameters and damage to the transducer. As a result, the shutdown of the wind farm continues until the damage is eliminated. High costs and losses of electrical energy result.

Overloading of generators and/or converters of a wind power installation results in too much kinetic power being delivered from the rotor to the generator or too much electrical power being converted, e.g. in excess of the maximum permissible rated power. occurs when flowing through a vessel.

For example, if the wind strength is too strong, or if too strong wind gusts occur, the rotational power of the rotor may increase significantly, possibly for a very short period of time, which is produced by the generator. may cause an increase in electrical output, which may damage the generator and/or may damage the converter, e.g. This is caused by excessively high currents flowing in the semiconductor elements of the converter.

Conventional closed-loop control of a facility based on the power curve of the facility compares the currently produced power output to a stored reference curve. The wind power plant is controlled in steady state by the pitch angle distribution of the rotor blades. Such closed-loop control cannot effectively prevent overload. This is because the pitch angle dispersion requires some time during which the output can increase further, which can damage the transducer.

Observing and measuring the electrical output of the generator is not sufficient to prevent or prevent overloading of the converter and/or generator. For example, monitoring and measuring the kinetic energy and/or the time derivative of the kinetic energy, for example the kinetic energy or power of the rotor, is not sufficient. That is, when an overload-indicative increase is measured, the pitch angle can no longer be adjusted immediately to still be able to effectively prevent overload.

That is, if a power increase in the generator or rotor is measured, adjusting the pitch angle of the rotor blades and/or braking the rotor will only take some time to effectively reduce the kinetic power received by the wind. Only after some time does an effective power reduction in the generator and/or converter occur. Damage to the converter or generator cannot be ruled out before the power reduction has taken effect, e.g. if a further increase in wind strength causes a further increase in power while the pitch angle is being adjusted. .

Nor can overload be effectively prevented by measuring wind strength. For one thing, local measurements, for example by anemometers in wind turbines, are subject to error. Furthermore, wind strength fields near wind turbines can be irregular or turbulent, and localized or point-like wind measurements can be difficult to obtain from the wind, especially during the occurrence of rapidly changing strong gusts. It is not suitable for effectively estimating the power delivered to the rotor of a wind power plant.

Measurement of the entire wind field in the vicinity of the wind farm, for example by means of LiDAR, is labor intensive and furthermore, estimation of possible overloads can only be made indirectly by calculation and evaluation of the measured data. .

Measurements of the wind field at long distances, for example by remote LiDAR at wind farms where wind turbines are located, are also unreliable. This is because, in the case of particularly strong gusts of wind, wind strength and wind direction can deviate significantly locally or cannot be accurately determined by distant wind field measurements.

Therefore, there is a need to measure or detect the increase in the wind force transferred from the wind to the rotor, especially without the use of anemometers, anemometers or LiDARs, in order to effectively prevent overloading of converters or generators. There is

Increased kinetic power transferred from the wind to the rotor causes deflection of the rotor blades. This is because the at least partially elastic rotor blades are exposed to greater forces. This deflection causes distortion of the rotor blades, especially in the region of the blade root portion of the rotor blades.

This bending moment is proportional to the measured strain. When a sudden change in strain occurs, the bending moment also changes abruptly.

The elasticity of the rotor blades creates a delay between strain and strong acceleration of the rotor. When the strain exceeds the threshold, according to the present disclosure, intervention occurs as quickly as possible. For example, damage to the converter/generator can be prevented. In the absence of intervention damage can already occur after 5 seconds due to overloading and damage to the transducer. The rotor blades can be adjusted in 3 seconds, but already after the start of adjustment the power drops sharply and damage/overload is immediately prevented.

By measuring the deflection of the rotor blades, it is possible to effectively measure the increase in rotor kinetic power and energy, or to prespecify and/or detect the resilience of the rotor blades, thereby , the overload of the converter or generator can be effectively prevented.

In particular, the mass inertia of the rotor/rotor blades already causes deflection of the rotor blades as the wind intensity increases, thereby causing the wind acting on the rotor blades to increase significantly before the electrical output at the generator increases significantly. power increases.

The use of at least one strain sensor 15 in the region of the blade root allows overload cases to be identified earlier. Based on the mass inertia of the rotor, the rotor accelerates and the deflection of the rotor blades increases before transferring the received energy to the generator. If the information obtained by the at least one strain sensor 15 is used, the installation can change the pitch angle of the rotor blades early, thereby preventing the onset of overload.

A strain sensor, such as strain sensor 15, can capture the increased deflection of the rotor blades before the rotor itself accelerates and outputs energy/power to the generator. The sensor device at the rotor blades thus recognizes the occurrence of a critical condition before an overload occurs. Conventional methods, on the other hand, only come into effect in the event of an overload and/or an increase in power at the generator. Thus, by using strain sensors to prevent overloading, more damage can be prevented in wind power installations.

By utilizing strain sensors, the occurrence of overloads can be identified before energy is directed into the system of the wind power plant. This also allows measures to be put in place to prevent damage before problems arise. This allows closed-loop control of a system that is proactive rather than a system that is purely reactive to the energy already introduced.

By using a signal that occurs earlier in time than the critical condition itself, for example a rotor blade deflection signal, the time window for introducing action to avoid damage is lengthened. The present disclosure is applicable to any wind power installation without intervening in the security chain.

For example, a threshold can be set for the strain sensor. If this threshold is exceeded, the wind power installation can be shut down or put into a reduced operating state for a short time.

The present disclosure measures or detects an increase in wind strength/speed with a time delay before this increase could introduce overload if no action is taken. This time delay is sufficient to effectively prevent an overload that would otherwise occur due to pitch angle adjustment. This time delay is caused, for example, by the mass inertia of the rotor.

An embodiment of the present disclosure is a method 200 (see FIG. 2) of controlling a wind power plant with a rotor having at least one rotor blade, the method measuring the strain of the at least one rotor blade. and modifying 220 the pitch angle of the at least one rotor blade at least in part based on the measured strain of the at least one rotor blade, wherein the strain of the at least one rotor blade is The measurement measures at least the strain in the root region of the rotor blade.

According to one embodiment, the measurement of the strain of the at least one rotor blade detects the deflection of the at least one rotor blade, which deflection signals the immediate future acceleration of the rotor.

This deflection is, in particular, a strain of the rotor blade above a predetermined threshold, for example at the root of the rotor blade. That is, not all strains are considered deflections, but strains above a threshold are considered deflections.

According to one embodiment, a change in the pitch angle of at least one rotor blade is made as soon as deflection is detected in order to prevent an immediate future acceleration of the rotor.

According to one embodiment, the pitch angle change prevents overloading of the generator and/or converter of the wind power plant, where the power transferred from the rotor blades to the generator and/or converter is limited. It remains.

That is, as soon as deflection is detected/determined/understood, i.e. strain exceeds a predetermined threshold for example, the pitch angle of the rotor blades can be changed thereby preventing an immediate future acceleration of the rotor. , in particular overloading of the converter and/or the generator can be prevented, wherein the power transferred from the rotor blades to the converter and/or the generator remains limited.

During normal operation of the wind power installation, distortion of the rotor blades is normal and acceleration of the rotor blades is also part of the normal operation of the wind power installation.

When wind with a certain wind speed enters the stationary rotor blades, the rotor blades distort and cause acceleration of the rotor. Acceleration is the angular acceleration of the rotor caused by torque on the rotor due to wind forces. At the same time, the rotor is braked by torque and/or friction acting in the opposite direction of the generator. As the angular velocity of the rotor increases under a constant wind speed, the torque produced by the wind decreases. This is because the relative velocity/motion of the wind towards the surface of the rotor blades is reduced. When equilibrium is reached between the torque produced by the wind and the torque produced by the generator and/or friction, the angular velocity of the rotor remains constant and the motional power flows from the wind to the generator, which is the electrical Generate output.

That is, during normal operation, the deflection of the rotor blades, for example at the root of the rotor blades, remains limited.

Excessively high wind speeds during gusts during storms, for example, cause relatively large strains on the rotor blades and/or rotor blade roots, and torque balancing occurs as the generator torque increases. This results in a higher electrical power being produced by the generator, which can, for example, cause damage to the converter and/or damage to the generator itself.

That is, if the rotor blade or blade root strain exceeds a threshold, subsequent overloading of the converter and/or generator can be foreseen if no action is taken. If the threshold is exceeded, the more the threshold is exceeded, the faster the overload occurs.

For example, the maximum rated power of the generator and/or the maximum rated power flowing through the converter is not exceeded when the subsequent balance between the wind torque and the generator torque occurs in the rotor, and thus in particular the converter and/or a threshold may be defined as an upper limit on the amount of strain before damage can occur in the generator.

The threshold may relate to the current rotational speed of the rotor. For example, large deflections of the rotor blades under high rpm may be more critical than at rotor standstill or at low rpm. This is because high strain at high rpm means that the already high power is further increased.

That is, exceeding the threshold is deflection of the rotor blade within the scope of this disclosure. Deflection occurs whenever the strain exceeds a threshold, where the threshold is either constant or a function of the current rotor speed and possibly another parameter of the wind power installation, e.g. It is related to the generator torque and/or the speed transmission ratio between the rotor and the generator, the electrical load and the like.

According to one embodiment, the strain measurement is performed by a fiber optic strain sensor 15 which is arranged in the root portion of at least one rotor blade and includes in particular a fiber Bragg grating.

According to one embodiment, the strain is measured for all rotor blades of the rotor and the pitch angle change is specifically based on the measured strain for all rotor blades.

According to one embodiment, the pitch angle change is additionally based on rotor power and/or rotational speed.

For example, blade root strain thresholds and corresponding detection of rotor blade deflection may also be related to rotor rotational speed.

For example, blade root strain thresholds and correspondingly detection of rotor blade deflection may not be related to rotor rotational speed, but changes in pitch angle are at least partially related to rotor power and/or Based on rotational speed. For example, in the case of relatively high rotor power and/or relatively high rotational speeds under constant deflection, i.e. exceeding a certain threshold strain in the root portion of the rotor blades, The amount of pitch angle change may be larger.

According to one embodiment, the pitch angle change is additionally based on the measured wind speed, in particular the wind speed measured by an anemometer or LiDAR.

Therefore, deflection detection and/or threshold exceeding can be supplemented with additional measurements to improve overload predictability. Thus, it is possible to distinguish between a single short-term wind impact on the rotor blades and whether repeated, high-intensity wind impacts can be expected. This allows, for example, a more differentiated decision whether to downregulate or shut down a wind power installation.

According to one embodiment, the strain measurement measures strain between a first point and a second distant point on the rotor blade, and measures strain between the first and second points. An optical fiber is provided across and includes, for example, a fiber Bragg grating.

Some embodiments relate to a wind power plant comprising a sensor for measuring strain of at least one rotor blade of a wind power plant and, based on the strain of the at least one rotor blade measured by the sensor, at least one a control unit configured to at least partially vary the pitch angle of the rotor blades, the control unit controlling the wind power installation according to the disclosed method.

Some embodiments relate to a wind farm comprising at least one wind power installation according to the present disclosure.

The use of glass fiber sensors, for example fiber Bragg grating sensors, allows the integration of strain sensors in the area of the blade root. This allows in particular an improved control of the individual wind power installations.

As soon as the strain exceeds the threshold, the installation is shut down or immediately controlled in order to effectively and advantageously avoid damage, e.g. to avoid overloading the converters and/or generators of the wind power installation. be able to. Preventive intervention becomes possible, whereas in the prior art a reactive response occurs only to the energy already introduced.

According to the present disclosure, each individual wind turbine can be effectively and cost-effectively controlled, thereby preventing damage to the individual wind turbines in particular.

Strain sensors, especially fiber Bragg grating sensors, are robust, long-lived, inexpensive, and easy to install.

For example, overloading and/or damage in converters/generators can be effectively prevented without using LiDAR. LiDAR comes with significant costs, and installing LiDAR for each individual wind farm is cumbersome and costly. Furthermore, LiDAR can be imprecise. This is because LiDAR captures spatially distant wind data, whereas actual local wind conditions can be turbulent and difficult to identify. In contrast, measurement of strain in the blade root region according to the present disclosure is accurate, effective, real-time feasible, and inexpensive.

It is also possible to measure the strain on individual rotor blades, whereas an anemometer, for example, can only provide inaccurate local wind measurements for the entire wind power installation. LiDAR also cannot measure or understand the strain of individual rotor blades. Thus, the present disclosure allows for more accurate estimation of rotor torque and/or pulsed acceleration of the rotor that may cause overload, and prevents overload or damage in, for example, a converter/generator. enable effective and immediate intervention to

Strain sensors of the present disclosure, such as optical waveguide sensors with fiber Bragg gratings, are more robust and long lasting than anemometer and/or LiDAR sensors.

The present disclosure does not require complex models and/or abstractions and/or laborious calibrations. A simple comparison with a threshold value is sufficient to measure/know the exact strain and/or deflection in the root region of individual rotor blades, which can lead to damage/overloads in e.g. transducers and/or generators. The load can be effectively blocked.

Anemometers are inaccurate even after laborious calibration, whereas in the present disclosure no calibration is required and/or calibration can be done quite easily. LiDARs are typically not part of individual wind turbines. Strain sensor mounting is straightforward and low cost, especially compared to LiDAR mounting.

Claims (11)

A method (200) for controlling a wind power installation (10) with a rotor having at least one rotor blade (17), said method comprising:
measuring (210) the strain of the at least one rotor blade;
varying (220) a pitch angle of the at least one rotor blade, at least in part, based on the measured strain of the at least one rotor blade;
contains
said measurement of said strain of said at least one rotor blade measures strain in at least the region of the root portion of said rotor blade (17);
A method (200). said measurement of said strain of said at least one rotor blade detects deflection of said at least one rotor blade, said deflection signaling an immediate future acceleration of said rotor;
The method of claim 1. making the change in the pitch angle of the at least one rotor blade as soon as the deflection is detected to prevent the immediate future acceleration of the rotor;
3. The method of claim 2. Said change of said pitch angle prevents overloading of generators and/or converters of said wind power plant, and the power transferred from said rotor blades to said generators and/or said converters remains limited. up to
A method according to any one of claims 1 to 3. performing said measurement of said strain by a fiber optic strain sensor located at said blade root portion of said at least one rotor blade and including a fiber Bragg grating;
A method according to any one of claims 1 to 4. measuring strain for all rotor blades of the rotor, wherein the change in pitch angle is based on the measured strain for all rotor blades;
A method according to any one of claims 1 to 5. said modification of said pitch angle is additionally based on power and/or rotational speed of said rotor;
A method according to any one of claims 1 to 6. said modification of said pitch angle is additionally based on measured wind speed, in particular wind speed measured by an anemometer or LiDAR;
A method according to any one of claims 1 to 7. Said measurement of said strain measures strain between a first point and a second remote point on said rotor blade, and an optical fiber extends between said first point and said second point. is being
A method according to any one of claims 1 to 8. A wind power generation facility (10), the wind power generation facility (10) comprising:
a sensor (15) for measuring the strain of at least one rotor blade (17) of the wind power installation;
a control unit (13) configured to at least partially vary the pitch angle of the at least one rotor blade (17) based on the strain of the at least one rotor blade measured by the sensor;
contains
The control unit controls the wind power installation according to the method of any one of claims 1 to 9.
A wind power plant (10). A wind power plant comprising at least one wind power installation according to claim 10 .

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